Yet another CRF 250 Build but its my first so... ;)

[fmxxx666]

Thanks Dave, I will of cause post every progress here.
Currently again waiting for some parts to get the Battery mount done.
Also waiting on 4AWG Cables and additional QS10 Connectors to get the Leads from Battery to Fuse to Batteryswitch to Controller to the correct length.
(little sidenote it was quiet a hassle to solder that large cables to a QS10 Connector when I was shortening the too long ordered Battery Cables)

It needed some extra heat usually I solder everything with 300 degree celsius but this time I had to go up to 450 degrees as there is such a large metal surface you need to heat up and I had to use a ton of solder xD
but now the cable is in a managable length




I have actually planned to do a California round Trip in a RV tackling all the typical tourist spots with Wife and Kid within the next 2 years.

 

[halg]

As far as thermal limits, the QS138 70H V3 is quite good. We ( probably 20+ DIY Bikes with pretty much the same QS138 70H V3, EM260S, 72V 50AH with an ANT smart BMS ) have not overheated the motor, We have overheated the controller without water cooling, and we have overheated the battery. The best counter for the battery is to get the BMS out of the battery box, go to Open Discharge (no BMS control of discharge), and /or make the battery so you can quick change it, and cool it during charge. The battery warms up while being used. If the BMS is inside the Battery box, it induces heat into the battery, your first moto or practice is fine. Come in to charge the warm battery, add more heat. Run second moto or practice, add more heat. Come in to charge a hotter battery and it will allow charge or not because it is already hot, or it will stop in the middle of a charge. It is slow to get the heat out of the battery box.
One friend has made it easy to change the battery, in a 2003 CRF450 . He has the whole build here on this forum Starting my bike build.

Hi Don. First off thanks for your contributions here. It has helped immensely in my planning.

I'm wondering what the real risk (if any) is of ordering my battery with open discharge. I can see how keeping the discharge current from flowing through the BMS and some of its relatively higher resistance parts helps reduce the heat. Which I think overall is a good thing in this application.

However, take a case like this:
1. Ride several laps - add heat
2. Charge - add heat
3. Repeat 1 and 2 some number of times adding heat
4. Charge - add heat and someone just happens to stop charging right below where the temperature BMS would normally cut off discharge if it was in the loop
5. Ride the bike all the way down - add heat that puts the battery above what the BMS would normally consider too hot if it was in the loop (Edit: I don't mean run the battery all the way down I mean down to the point where the controller shuts the bike down or goes into limp mode)

In step 5, with an open discharge battery, is it accurate to say that the battery would continue to discharge normally and continue adding heat even though it is above what the BMS would normally consider too hot? It seems to me it would.

Finally, do you know what temperature the ANT BMS that come from Amorge disconnect charging? If the answer to the above question is yes, then I'd like to know to tell people to bring it back if that is exceeded while riding.

There is risk everywhere in life. Heck even riding dirt bikes at all is a relatively high risk activity. I just usually like to believe I understand the risks with anything I build.

Thanks again!

 

[fmxxx666]

Hi @halg
I looked into this as well before I decided to go with an open discharge battery.

My ANT BMS still monitors the battery’s temperature and it will beep when hitting the threshold.

You can define the temperature threshold yourself in the ant bms app.

I have no experience yet with what temperatures it reaches under heavy load as I am still yet to finish my build and it’s freezing cold outside here at the moment so even on my test runs heat is the last thing I care of atm


my controller display on the handlebar shows me controller and motor temperature and for the battery I would have to look up on my phone to get an exact figure but to regularly hand feel the battery’s temperature between laps to get an idea what type / length of riding would get it to what kind of heat is still on my list for the learning curve about this subject.

When I look into the specs of my battery cells (molicel p45b)
They have a charge cut off at 70 degrees Celsius
And they have a discharge cut off at 80 degrees Celsius.

So I would setup my ant bms to warn me at somewhere 50-60 degrees Celsius as this is actually already pretty hot in my eyes.

 

[halg]

Hi @halg
I looked into this as well before I decided to go with an open discharge battery.

My ANT BMS still monitors the battery’s temperature and it will beep when hitting the threshold.

You can define the temperature threshold yourself in the ant bms app.

I have no experience yet with what temperatures it reaches under heavy load as I am still yet to finish my build and it’s freezing cold outside here at the moment so even on my test runs heat is the last thing I care of atm


my controller display on the handlebar shows me controller and motor temperature and for the battery I would have to look up on my phone to get an exact figure but to regularly hand feel the battery’s temperature between laps to get an idea what type / length of riding would get it to what kind of heat is still on my list for the learning curve about this subject.

When I look into the specs of my battery cells (molicel p45b)
They have a charge cut off at 70 degrees Celsius
And they have a discharge cut off at 80 degrees Celsius.

So I would setup my ant bms to warn me at somewhere 50-60 degrees Celsius as this is actually already pretty hot in my eyes.

great to know that it beeps. thanks. something you could actually hear b/c you are riding an electric bike!

i went (relatively) cheap with my controller which is a votol em260sgtp so i'll be figuring how how to monitor all those temps since it did not come with a display.